[mythtv] Solution to CableCARD problem?

[Tim Moore]

I'm new to MythTV, so please excuse me if this has already been addressed.
I understand the problem with CableLabs certification, and how it will be
impossible for an open source solution to obtain it.  However, I've been
doing a lot of research into this, and it seems to me that there is a
solution that has been overlooked.

 

CableLabs won't certify a MythTV solution because it would be impossible in
an open source solution to prevent access to the decrypted video stream.
The reason that Vista can obtain it is because of the closed DRM
implementation that MS has built into the operating system and into Windows
Media Player.  There really is no way to get around this CableLabs
requirement, so I propose that the solution is a modified architecture for
MythTV that will works with it.

 

Essentially, the video path and the control path of the system need to be
separated.  The video path needs to be closed and "secure" (or, that is,
meet CableLabs requirements.  We all know that nothing is 100% secure.).  It
is not good enough to use some video adapter with CableCARD slots (such as
the ATI card that Dell is using for its premium cable-ready TV), which
decrypts the video signal and passes it to the operating system and media
player software.  This approach, as we have seen, requires CableLabs to
trust the operating system, the media center software, and the hardware.
For the ATI card to work on the Dell system, the ATI drivers (written by
Microsoft, by the way) check for a code in the BIOS to confirm that it is
connected to approved hardware.  Getting CableLabs certification costs over
$100,000 per system, so this approach rules out small system builders, even
if they are using Vista.  For open source solutions, it rules it out
altogether.

 

However, we are starting to see hardware manufacturers build single-chip DVR
solutions.  The Broadcom BCM7118
<http://www.broadcom.com/products/Cable/Cable-Set-Top-Box-Solutions/BCM7118>
is one such device.  This board contains not only a CableCARD interface, but
also DCAS support which should eventually supersede CableCARD with a
downloadable conditional access system (reducing the high upgrade and
support costs for cable companies, and/or users, caused by the current
hardware-only solution).  The BCM7118 interfaces directly to its own hard
disk, securely storing encrypted programming.  It contains all the critical
components of a premium cable-ready DVR; authentication, authorization,
decryption, decoding, storage, graphics, sound and control.  You can make a
stand-alone DVR from this system, with the addition of a case, hard disk,
and some basic supporting electronics.  As a complete and closed system,
theoretically, the BCM7118 should be able to achieve CableLabs
certification.  However, I haven't seen it on the CableLabs approved list so
I have emailed Broadcom to find out.  I'll let you know what I hear.
Hopefully, it's in the works.

 

The BCM7118 supports an API that allows a connected system to control it.
So, MythTV could be modified to use this API to control the BCM7118.  I'm
sure there must be a graphics card out there that can take the output of the
BCM7118 and superimpose on it graphics from the PC, thereby adding a
capability to add EPG and other graphics from MythTV.  Since the decrypted
TV signal is not passed to the MythTV software or operating system, there is
no risk of it being copied.  That is, no more than the output of any other
cable box.

 

So, the solution is not to make decryption part of a MythTV system, but to
make MythTV a control solution for a bare-bones DVR that is installed inside
the PC chassis.  Of course, MythTV could still work in the traditional mode
for unencrypted media.  I realize that this means that the entire solution
is no longer 100% open source, but then what system is when you take into
account the firmware in the supporting hardware?  The important thing is
that all of the high-level control software remains open source, and that is
where the value is added.

 

There is still one small snag.  Broadcom doesn't yet make a single-chip
system with HD output (although it can downscale HD to SD).  I'm sure that
can't be too far away, and I have emailed them to find out.

 

I think that if the development community can get behind this (and if
CableLabs will certify single-chip/board DVRs, as I hope) then MythTV can
remain a viable alternative to Vista.  If not, then it will surely die as
new cheaper alternatives to Tivo become available and more Vista systems get
certified.

 

 

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mythtv.org/pipermail/mythtv-dev/attachments/20070708/38246d8e/attachment.htm